A transverse harmonic wave on a string is described by \(y(x,t) = 3.0 sin ( 36t + 0.018x + {\pi \over 4})\) where x and y are in cm and t in sec. The positive direction of x is from left to right.

What is the shortest distance between two successive crests in the wave?

1. 1.3 m

2. 3.0 m

3. 2.5 m

4. 3.5 m

For the travelling harmonic wave, \(y(x,t) = 2.0\ cos\ 2\pi (10t - 0.0080x + 0.35 )\) where x and y are in cm and t is in seconds. The phase difference between the oscillatory motion of two points separated by a distance of 4 m will be:
1. \(0.8\pi\ rad\)
2.  \(\pi\ rad\)
3. \(6.4\pi\ rad\)
4. \(4\pi\ rad\)